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Original Report |
1
Department of Angiography and Interventional Radiology, University Clinic of
Radiodiagnostics, General Hospital Vienna,
Währinger Gürtel
18-20, A-1090 Vienna, Austria.
2
Department of Cardio-Thoracic Surgery, University Clinic of Surgery, General
Hospital Vienna, A-1090 Vienna, Austria.
Received December 29, 2000;
accepted after revision June 5, 2001.
Address correspondence to J. Sailer.
Abstract
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CONCLUSION. Endovascular treatment of acute and chronic aortic type B dissections and penetrating ulcer is a minimally invasive method with a low complication rate that could be considered a feasible alternative to surgical repair. Depending on the length of the dissection, we recommend the placement of two overlapping stent-grafts in the thoracic aorta to stabilize the affected thoracic aorta over a longer distance. This might provide a reliable sealing of the entry tear and should prevent further communication between the true lumen and the false lumen.
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The preferred treatment for asymptomatic patients with acute aortic type B dissection has been conservative therapy with antihypertensive drugs and beta-blockers [4]. However, aortic dissections are associated with a high mortality rate (36-72% within 48 hr of diagnosis) [5]. Cases complicated by progression, impending rupture, refractory hypertension, localized false aneurysm, continued pain, or end-organ ischemia have been reported to be an indication for surgical therapy. Such therapy, however, has been associated with high mortality rates (survival rate, 40-49% after 10 years) [1]. For patients undergoing either medical therapy or surgery, the intermediate and long-term prognoses are unsatisfactory.
Therapeutic strategy has changed greatly in the past several years, with the development of transcatheter stent-graft treatment for aortic aneurysms [5, 6]. However, to our knowledge, few results of the use of stent-grafts to treat thoracic dissection or penetrating ulcer have been reported [7, 8]. The basic purpose of using stent-grafts for these indications is to completely cover the primary entry tear and to eliminate most of the inflow to the false lumen, thus promoting thrombosis of the false lumen [5].
The aim of this study was to report our clinical experience and short-term results in using commercially available stent-grafts to perform endovascular repair of acute and chronic aortic type B dissections and penetrating ulcers. In addition, we report changes in the true lumen and the false lumen with follow-up after the interventional therapy.
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Diagnosis was made on the basis of a digital subtraction angiography (Multistar; Siemens, Erlangen, Germany) and helical CT scans with three-dimensional reconstruction (Somatom Plus4 scanner; Siemens) in all patients. Required anatomic criteria for stent-graft insertion were an entry site at least 1 cm distal to the left subclavian artery and suitable access through the iliac or femoral artery. The maximum diameters of the true lumen and the false lumen of the thoracic aorta were evaluated from cross-sectional CT scans on a picture archiving and communication system workstation (Sienet Magic View 1000; Siemens), measured along a line perpendicular to the intimal flap.
In four patients, the abdominal aorta was affected by the dissection. In one patient, the inferior mesenteric artery and right renal artery were perfused from the false lumen; in all other patients, abdominal vessels were perfused from the true lumen of the dissected aorta. The mean time between diagnosis and stent-grafting was 4.75 ± 3.7 days (range, 1-10 days) for the acute dissections (n = 9) and 42 ± 5.2 days (36-45 days) for the chronic dissections (n = 2). All patients were hemodynamically stable and none had abdominal organ ischemia. All data were evaluated retrospectively.
Technique
The interventional procedure was performed in nine patients using a GORE
Thoracic EXCLUDER endoprosthesis (W. L. Gore; Sunnyvale, CA). This device
consists of an ultrathin expanded polytetrafluoro-ethylene graft with an outer
self-expanding ninitol support structure and is inserted with a catheter-based
delivery technique. In one patient, a TALENT endoprosthesis (Medtronic;
Sunrise, FL) was used and in one other patient a VANGUARD endoprosthesis
(Boston Scientific; Natick, MA) was used. These stent-grafts were selected
according to availability and specific features such as length and diameter
bearsprings at the proximal end of the stent-graft, which enable overstenting
of major branch vessels.
Standard antihypertensive medication was given before deployment of the TALENT and the VANGUARD devices. Reduction of the systolic blood pressure was not considered necessary when using the EXCLUDER stent-graft, because with deployment this device spreads within milliseconds from the center outward. Interventions were performed under general anesthesia in a specially designed endovascular suite by a team of interventional radiologists and cardiovascular surgeons. The femoral (n = 4), distal (n = 5), or proximal iliac artery (n = 2) was surgically exposed. In one patient an aortobifemoral prosthesis had to be used for vascular access. After the insertion of the appropriately sized introducer sheath (22-24 French), a superstiff 0.035-inch guidewire (Backup Wire; Boston Scientific) was placed into the aortic arch under fluoroscopic guidance. Before insertion of the stent-graft into the optimal position, 5000 IU of heparin were administered, and intraoperative anti-bacterial medication was given prophylactically. After deployment, the grafts were seated against the aortic wall using a balloon catheter. Finally, angiography of the thoracic aorta was performed to confirm the position of the device relative to the entry tear and to exclude the presence of any endoleaks.
Follow-Up
Follow-up investigations were performed between 2 days and at least 6
months after the intervention (2-360 days; median, 256 days). The first
follow-up was performed after discharge in all patients. We could not perform
a second and third follow-up in all patients; the second follow-up was
realized in nine patients (82%) and a third in six (67%) of those nine
patients. For follow-up investigation, helical CT scans of the aorta were
analyzed for correct placement of the stent-device and the occurrence of
endoleaks (White et al. [9]).
Diameters of the true lumen and the false lumen were measured on
cross-sectional CT scans as they were for diagnosis. Clinical data concerning
early mortality and morbidity rates were available in all patients over a
period of at least 30 days.
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In eight patients (73%), deployment of two stent-grafts in an overlapping way was essential to cover a secondary entry. In one of these patients, stent-graft retraction during deployment required the use of a second device. No patient required adjunctive treatment, blood transfusion, or inotropic support. In the two patients with a penetrating ulcer as part of a true aneurysm of the thoracic aorta, total exclusion from blood flow was achieved. In one patient, we diagnosed a retroperitoneal hematoma within 24 hr after the intervention. It was caused by bleeding of the access site and required surgical evacuation.
No other early complications, such as stroke, paraplegia or paraparesis, myocardial infarction, or pulmonary insufficiency occurred; the intensive care unit stay was less than 24 hours for all patients. All patients presented a postimplantation syndrome, including inflammation and slight back pain, which resolved in 5-25 days. The mean time of hospitalization was 10.18 ± 4.33 days.
The mean diameter of the implanted stent-grafts (n = 21) was 37.52 ± 3.7 cm (range, 26-40 cm) and the mean length was 15 ± 5.0 cm (range, 5-20 cm). The mean length of the dissections was 22.31 ± 24.6 cm (range, 3-70 cm) and the mean length of the penetrating ulcer was 3.27 ± 1.1 cm (range, 1.6-4 cm).
During follow-up investigations, the mean diameter of the false lumen of the dissected aorta decreased from 2.34 ± 0.6 cm (range, 1.7-3.2 cm) to 0.7 ± 0.4 cm (range, 0.2-1.0 cm) (-70%), and the true lumen increased from 1.56 ± 0.5 cm (range, 0.8-2.3 cm) to 4.10 ± 0.6 cm (range, 3.5-4.7 cm) (+163%). For penetrating ulcers, the equivalent data were from 1.08 ± 0.7 cm (range, 0.4-2 cm) to 0.35 ± 0.2 cm (range, 0.2-0.5 cm) (-68%) and from 3.88 ± 1.5 cm (range, 2.6-6 cm) to 4.60 ± 1.1 cm (range, 3.8-5.4 cm) (+19%). In eight patients (73%), total thrombosis of the false lumen was achieved, and in three patients (27%), a partial thrombosis was achieved (Table 1).
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An endoleak was diagnosed in one patient at the first follow-up; however, it was not evident at the second. In one patient, progression and increase of the dissection into the abdominal aorta was observed, despite precise sealing of the entry tear in the thoracic aorta (Fig. 1A,1B,1C,1D,1E,1F,1G,1H). Perfusion of the inferior mesenteric artery and the right renal artery from the false lumen of this patient did not change during follow-up. We did not encounter any late complications or death during follow-up.
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The graft serves to exclude flow through the initial tear in the intima and redirect aortic blood flow exclusively into the true lumen reestablishing perfusion of aortic branches affected by the spreading dissection. This can also avoid a true lumen collapse, which was investigated experimentally [10, 11]. Interventional alternatives such as balloon fenestration of the flap are often technically difficult, require multiple steps, and are time-consuming [12].
In agreement with Nienaber et al. [7] and Dake et al. [8], a minimum length of 1 cm is mandatory to achieve sufficient anchorage of the stent-graft. We preferred the use of the GORE Thoracic EXCLUDER because of its higher flexibility during introduction into the iliac arteries and its rapid deployment from the center outward leading to exact placement without dislocation.
In eight patients (73%) we placed a second stent-graft. Our goal was not only the complete sealing of the entry and continuous perfusion of the false lumen, but also the stabilization of the affected thoracic aorta over a longer distance. The arterial supply of the distal spinal cord usually originates from one of the intercostal arteries between the eighth thoracic and the first lumbar vertebrae; stent-graft placement of the distal thoracic aorta should be avoided to prevent spinal ischemia.
Effective treatment of penetrating ulcers is a life-saving strategy, because the risk for aortic rupture (40%) is significantly higher in these patients than in patients with aortic type B dissection (3.6%) [2]. Because of the small size of a penetrating ulcer, sealing of the perforation with a stent-graft is obvious and recommended [5]. In our four patients, this approach lead to thrombosis of the ulcers (Fig. 2A,2B). We consider this strategy an optimal treatment for acute penetrating ulcers of the thoracic aorta.
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We achieved a decrease of the false aortic lumen in all but one patient, accompanied by an increase of the true lumen (Table 1), and we did not observe ischemic symptoms after stent-graft implantation, even when using two devices. In three patients (27%), we observed partial thrombosis of the false lumen, which is still advantageous in preventing enlargement of the false lumen. Complete sealing of the entry tear is considered the final goal of endovascular aneurysm repair. We report the appearance of an endoleak in only one patient, diagnosed in the CT scan at discharge. This endoleak was thrombosed within 3 months.
In the treatment of acute and chronic aortic type B dissections or of acute penetrating ulcer, we propose the use of a stent-graft. Restrictions are primarily related to unfavorable anatomic conditions such as an inadequate vascular access or an inappropriate distance between the entry tear and the left subclavian artery. At the moment, we believe that hemodynamically unstable patients should be treated surgically as well, because we consider rupture an indication for surgical repair. In hemodynamically stable patients without organ malperfusion, current treatment options are stent-graft placement versus conservative therapy. In patients with dissection complicated by malperfusion of abdominal or lower limb arteries, it is not known whether surgery is necessary or reperfusion can be treated by stent-graft implantation only. Randomized trials are necessary to answer these questions.
In conclusion, the purpose of our feasibility study was to determine whether endovascular treatment in aortic type B dissection and penetrating ulcer causes thrombosis of the false lumen and therefore prevents secondary aneurysm formation and rupture. Although we present short-term results of a small sample of patients, we consider stent-graft placement a feasible and minimally invasive treatment with a low complication rate for patients with aortic type B dissection and penetrating ulcer.
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